[Mp4-tech] Can't decode this mp4 file, but mplayer plays it, why?

[Max Grießl]

Using the option -vo yuv4mpeg for mplayer a file stream.yuv is written.
This file contains the raw yuv420 images. But every frame has a small
header. These headers may be removed with the following command:
perl -p -e's/YUV4MPEG.*\n//g' stream.yuv | perl -p -e's/FRAME\n//g' >
video.yuv
Regards,
Max Griessl
Bheemarjuna Reddy Tamma wrote:
> Hi All,
> 
> I am using ffmpeg for a research project in video multicasting over ad
> hoc wireless networks. I am facing the following problem:
> 
> I am able to play the highly distorted mp4 files using mplayer,
> however when I try ffmpeg on them to decode them into yuv format (I
> need that to compute the psnr). It gives the following output :
> --
> [devesh mcn test_psnr]$ ~/ffmpeg/ffmpeg -i try_2_0.mp4 try.yuv
> FFmpeg version CVS, Copyright (c) 2000-2004 Fabrice Bellard
>  configuration:
>  libavutil version: 49.0.0
>  libavcodec version: 51.2.0
>  libavformat version: 50.2.1
>  built on Feb 23 2006 00:09:27, gcc: 3.3.3 20040412 (Red Hat Linux 3.3.3-7)
> Input #0, mov,mp4,m4a,3gp,3g2, from 'try_2_0.mp4':
>  Duration: 00:00:13.3, start: 0.000000, bitrate: 379 kb/s
>  Stream #0.0(und),  7.50 fps(r): Video: mpeg4, yuv420p
> Output #0, rawvideo, to 'try.yuv':
>  Stream #0.0,  7.50 fps(c): Video: rawvideo, yuv420p, q=2-31, 200 kb/s
> Stream mapping:
>  Stream #0.0 -> #0.0
> [rawvideo @ 0x82fcd68]dimensions not set
> Could not write header for output file #0 (incorrect codec parameters ?)
> [devesh mcn test_psnr]$
> --
> These files are available at http://www.cs.iitm.ernet.in/~dvagr/mp4files
> Mplayer can play each one of them, but ffmpeg doesn't work (ie gives
> the same error message as shown above), and xvid_decraw segfaults.
> 
> These files were produced using the etmp4 tool, as given on the site
> http://www.tkn.tu-berlin.de/research/evalvid/EvalVid/docevalvid.html.
> However, ffmpeg is able to decode slighly less distorted files
> comfortably, it only seems to give up on more distorted files.
> 
> If ffmpeg can't do the job, is there any way I can make
> mplayer/mencoder to dump yuv420p files from this mp4 video ?.
> 
> Thanks, eagerly awaiting your reply. Any pointers/advise/help would be
> highly appreciated.
> 
> regards
> Arjun Reddy
> 
> --
> T. Bheemarjuna Reddy
> Ph.D. Student
> HPCN Lab
> Dept. of Computer Science & Engg.
> IIT Madras, INDIA
> Mobile: +91-9444206507
> http://hpcn.cs.iitm.ernet.in
> 
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-- 
Max Griessl
Software Design
Holon Technology GmbH (a DynaPel Company)
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